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We present photometric and spectroscopic observations of the nearby Type IaSN 2019yvq, from its discovery $\sim$1 day after explosion to $\sim$100 daysafter its peak brightness. This SN exhibits several unusual features, mostnotably an extremely bright UV excess seen within $\sim$5 days of itsexplosion. As seen in Swift UV data, this early excess outshines its "peak"brightness, making this object more extreme than other SNe with early UV/blueexcesses (e.g. iPTF14atg and SN 2017cbv). In addition, it was underluminous($M_B=-18.4$), relatively quickly declining ($\Delta m_{15}(B)=1.35$), andshows red colors past its early blue bump. Unusual (although not unprecedented)spectral features include extremely broad-lined and high-velocity Siabsorption. Despite obvious differences in peak spectra, we classify SN 2019yvqas a transitional member of the 02es-like subclass due to its similarities inseveral respects (e.g. color, peak luminosity, peak Ti, nebular [Ca II]). Wemodel this dataset with a variety of published models, including SN ejecta -companion shock interaction and sub-Chandrasekhar mass WD double detonationmodels. Radio constraints from the VLA place an upper limit of $(4.5 - 20)\times 10^{-8}$ M$_{\odot}$/yr on the mass-loss rate from a symbioticprogenitor, which does not exclude a red giant or main sequence companion.Ultimately we find that no one model can accurately replicate all aspects ofthe dataset, and further we find that the ubiquity of early excesses in02es-like SNe Ia requires a progenitor system that is capable of producingisotropic UV flux, ruling out some models for this class of objects.

A Bright Ultraviolet Excess in the Transitional 02es-like Type Ia Supernova 2019yvq